Hello again! Glad to see that some stuff is working for you! I've tried creating some events to spawn where one was using autonomous movement random and the other was using autonomous movement fixed. I was unable to replicate your issue. If you could show me what's happening along with the events in question that would help clear things up.
Steps I took:
Created 2 events on a spawn map.
One using Autonomous movement Random and the other using Autonomous movement Fixed.
I spawned the random event first and let it move around for a little bit.
I unspawned the random event.
I then spawned the Fixed event.
resulting in the fixed event staying in place on the tile it was spawned on without moving.
I did this a few more times alternating between the two events and couldn't get it to break.
I can dig deeper with more information.
Thank you and Good Luck!